1. Field of the Invention
The present invention relates to an auxiliary lock with a control plate for preventing unlatching from outside.
2. Description of the Related Art
Taiwan Utility Model Publication No. 182885 issued on Apr. 21, 1992 discloses an auxiliary lock having a cavity for receiving a spring and a steel ball. The steel ball may bear against an inner toothed face of a toothed ring which is mounted in a knob to rotate therewith. Nevertheless, unintentional rotational movement relative to the knob may occur and thus result in undesired locking when in use.
Taiwan Utility Model Publication No. 346987 issued on Dec. 1, 1998 discloses an auxiliary lock having a latch plate mounted to a mounting plate. An engaging wheel is provided in a notch in the latch plate to prevent rotational movement of the engaging wheel. The latch plate is supported by elastic members so as to be moved upward or downward to a proper level. Nevertheless, the elastic members may have fatigue or be worn and thus cannot retain the latch plate in place. As a result, the control plate may fall and thus cause problem to operation.
The present invention is intended to provide an improved auxiliary lock that mitigates and/or obviates the above problems.